The present disclosure generally relates to fluid fittings and, more particularly, to an improved fitting with sequential sealing action. In one embodiment, a fitting includes a connector body having a sleeve that receives a tube or pipe therein and includes a plurality of radially extending seals for sealing and mechanically connecting to the tube or pipe when a swage ring is axially installed on the sleeve. In particular, the seals include a main seal which is set first, an inboard seal which is set second, and an outboard seal which is set third. After the outboard seal is set, a kickdown of the main seal also occurs. The improved fitting will be described with particular reference to this embodiment, but it is to be appreciated that the improved fitting may relate to other similar environments and applications.
Various types of fittings have been developed for joining tubes and pipes to other tubes and pipes, or to other fluid apparatus such as pumps, fluid motors, actuation cylinders, etc. For thin walled tubing or pipe, various types of fittings are used which compress against the outside diameter of the tube or pipe to create a seal. One particular type of such a fitting includes a swage ring which is forced over the fitting to compress it radially inwardly against the tube or pipe to create a seal. Generally, this type of fitting has one or more circumferential teeth or ridges on its inside diameter which, when compressed inwardly by a swage ring, engage the outside diameter of the tube or pipe to create one or more leak-tight mechanical connections or joints between the tube or pipe and the fitting. This engagement of the sealing teeth of the fitting with the tube or pipe causes the pipe to be deformed radially inwardly, with the coupling body of the fitting located externally about the tube or pipe.
Examples of such mechanically attached fittings are provided in U.S. Pat. Nos. 4,482,174; 5,110,163; 5,114,191; and 6,692,040. One example installation tool employable for attaching these types of fittings to a tube or pipe is described in U.S. Pat. No. 5,305,510. All the teachings and substance of these patents are hereby expressly incorporated by reference into the present application.
The types of fittings described in the preceding paragraphs are often designed so that the sealing ridges sequentially engage the tube or pipe upon which the fitting is being installed. Such sequential engagement reduces the installation force required to move the swage ring from an outboard position to a fully installed inboard position. This is due to the installation tool only being required to provide enough force to do the work necessary to cause deformation, and thus sealing engagement with the tube or pipe, at one sealing ridge location at a time. Performing the fitting installation at two or more sealing teeth locations simultaneously would require more force as more work would have to be done per increment of travel of the swage ring.
Sometimes the sealing ability of a fitting can be diminished, particularly as a consequence of two factors: (1) sequential tooth or seal engagement and (2) pipe radial deformation. For example, engagement of a second sealing tooth subsequent to engagement of a first sealing tooth, arid the attendant pipe deformation caused by the subsequent engagement, may reduce the loading force between the first sealing tooth and the tube or pipe. In this example, the loading force reduction due to the subsequent engagement of the second tooth results from the pipe being pushed away from the first tooth. In an extreme case, this may result in a gap being formed between the first sealing tooth and the tube or pipe and/or may result in diminished effectiveness of the seal between the first sealing tooth and the tube or pipe, particularly under the influence of an applied mechanical load such as bending and torsion.
The assignee of this application, Lokring Technology Corporation, manufactures, sells and/or distributes a variety of such sequential fittings. These fittings often include three (3) circumferential teeth or ridges, typically referred to as seals, including a main seal, an inboard seal and an outboard seal. As already discussed, the seals extend radially inward from an inside diameter of the fitting's body and are compressed inwardly by a swage ring axially installed on an outside diameter of the fitting body to create a leak-tight mechanical connections or joints between each seal and a tube or pipe received inside the fitting body to which the fitting is being connected. The engagement of the seals with the tube or pipe causes the same to be plastically deformed radially inward at the location of engagement with the seals.
The particular configuration of the fitting body and/or the swage ring often determines the order in which the seals (including the main, inboard and outboard seals) are forced into deforming contact with the tube or pipe. Applicant's three-seal fittings can employ different order sequences (i.e., the order in which the seals make deforming contact with the tube or pipe) for different fittings and particularly different sized fittings. In most cases, the main seal is the first of the seals forced into deforming contact with the tube or pipe, irrespective of the size of the fitting. However, the next seal to make deforming contact varies among various fittings of Lokring. Thus, in some fittings the outboard seal makes deforming contact immediately after the main seal and in other fittings the inboard seal makes deforming contact immediately after the main seal and before the outboard seal.
Some three-seal fittings of Lokring are configured for applying a kick down force to the main seal. Thus, after a particular surface of the swage ring forces the main seal into deforming contact with the tube or pipe, a second, diametrically smaller surface of the swage ring further forces the main seal into the tube or pipe. Like the order in which the inboard and outboard seals deforming contact the tube or pipe, the sequential order in which the kick down force is applied to the main seal varies from fitting to fitting. In some fittings, the main seal deformingly contacts the tube or pipe first, the outboard seal deformingly contacts the tube or pipe second, the inboard seal deformingly contacts the tube or pipe third and the kick down occurs last. In other fittings, the main seal deformingly contacts the tube or pipe first, the kick down effect-occurs second, the inboard seal deformingly contacts the tube or pipe third and the outboard seal deformingly contacts the tube or pipe last.
Accordingly an issue to be addressed is that of obtaining the optimal benefit of sequential engagement of the sealing teeth, particularly in a fitting wherein a main seal, an inboard seal and an outboard seal are provided with a kickdown of the main seal, while reducing or eliminating any associated reduction of load force between the tube or pipe and sealing teeth on the sealing teeth that were engaged early in the engagement sequence.